Rie trevoux



Patented Sept. 12, 1922.

uNrrEo STATES PATEN T OFFICE.

LAURENT EMILEMARIE TREVOUX, or PETIT-QUEVILLY, FRANCE, ASSIGNOR 'ro L'A soom'ri: ANONYME DE PRODUITS CHIMIQUES ETABLISSEMENTS MALE'TRA, or

PETIT-QUEVILLY, FRANCE. rRocnss FOR THE rRonUc'rIoN or No Drawing. Application filed May 31,

T all whom it may concern:

Be it known that I, LAURENT EMILE MA- RIE TRRvoUx, citizen of the Republic of France, and resident of. Petit-Quevilly, France, (post-office address-Petit-Quevilly, Seine-Infrieure), have invented a new and useful Process for the Production of Acetaldehyde from Acetylene, which improvements are fully set forth in the following specifica tion.

This invention relates to a process for the production of acetaldehyde from acetylene.

For the synthetic production of acetaldehyde when a current of acetylene is passed over a mercuric salt in an acid medium, the activity of the mercuric catalyzer rapidly diminishes and the absorption of the acetylene becomes slower in proportion as the reduction of the mercuric salt progresses, and stops completely when the mercuric salt is reduced to the state of a greyish powder. At this moment, whatever method is employed, it is necemary to regenerate the mercuric salt by oxidation.

In the process which is described in my copending application for United States Patent Serial No. 368,439, filed March 24:, 1920, the activity of the catalyzing agent is maintained by adding to the mercury constituting such agent or reduced mercury an ox.-

idizing substance, such as ferric oxide or another suitable oxidizing agent.

This addition allows of rolonging the action of the mercury indefinitely without it being necessary to regenerate same. When the oxidizing agent is exhausted the liquid is decanted, and suitable proportions of fer ric oxide and sulphuric acid are added to the residual grey powder. From tlme to .40 time the ferroso-ferric salt of the reaction liquid is tested by means of potassium permanganate and the ferric oxide is renewed when necessary.

Although the preparation of ferric oxide is relatively cheap, instead of renewing it every time with fresh liquid containing ferric oxide, use is made of a reoxidized liquor comin from a previous reaction. The re-' oxidation of the ferrous salt into ferric salt to can be efiected either by boiling with nitric acid or preferably by electrolysis.

This last method is employed in'the present application.

ACETALDEHYDE ACETYLENE.

- acts the reaction and prevents the formation of the metal-organicv compound which generates the aldehyde. Moreover only small amounts of aldehyde and acxetic acid are obtamed. It is for this reason that these processes have not been emplo ed in practice and that up to the present as gar as I know it has not been pomible to efi'ect directly the synthesis of acetic acid without first producmg the aldehyde and thereafter oxidizing same. Neither has it been thought possible that, by regeneratin the ferric salt within. the catalyzer by t e electrolytic operation, a practical result can be obtained. It is necessary for the oxygen carriers to be added to the reaction liquid in such a way that without preventing, retarding or diminishing the formation of aldehyde they are ada ted, if suit-ably controlled, to act on the fbrrosoferric salt by constantl maintaining an excess of ferric oxide in t e reactionli uor.

On the other hand it is not possib e without great inconvenience to directly electrolyze the residual reaction li uor, because this does not merely contain a errous salt only. The residual reaction liquor (which is slightly coloured brown after the acetylene has been passed therethrough) always contains, in addition to the ferrous salt, a variable small amount of acetaldehyde (uncondensed as well as the mercuric salt in solution. f the residual liquor of reaction is directly electrolyzed in a suitable electrolyzer for example consisting of a receptacle of lead witha cathode of the same metal, it will be noticed that, after regeneration, a large deposit of lead salt is produced. More over, the cathode has become amalgamated and partly disintegrated.

1. A part of the acetaldehyde has been transformed by the electrolytic om'datifln into acid. This acid combines with peroxide of lead and sulphuric acid, in solution in the not ferrous liquor, to form lead sulphate and content of acetic acid is sufiicient to start the reaction.

2. The cathode is attacked by reason of the fact that the residual reaction liquor contains a little dissolved mercury salt.

Although mercurysulphate is very slight- 1y soluble, the small amount of the salt in solution is electrolyzed and deposits on the cathode, which it amalgamates. The same inconvenience occurs with a cathode of copper or other metal.

According to the present invention, the

operation is effected in the following way.

Acetaldehyde is prepared until the catalyzer is exhausted and the ferric salt has been reduced. Thereupon' the residual reaction liquor is separated by decantation. This liquor contains ferrous salt a l ttle dlS- solved mercury salt and acetaldehyde.

The aldehyde is first removed by heating or preferably by evacuation. If, in order to remove the aldehyde, the liquid were heated to a relatively high temperature, part of said aldehyde would be resinified, and would yield tars. It is therefore preferable to operate in vacuo at a temperature below 50 (3., so as to eliminate the aldehyde without polymerization. The aldehyde vapours are recovered by 'suitable means, such as condensation or in the form of stable paraldehyde.

Thereupon the ferrous liquor from which the aldehyde has been removed is brought into contact with iron filings which completely precipitate the mercury. According to the working temperature employed, the mercury sulphate is transformed more or less quickly 1nto mercury, the reduction being complete in about two hours at C. The mercury is deposited at the bottom of the receptacle and the liquid is' decanted. The liquor thus contains only ferrous sulphate in sulphuric acid solution and it is ready to be electrolyzed.

The above series of operation may be re-' versed.

The .electrolyzer consists preferably of a lead receptacle with lead electrodes; It is essential to maintain the density of the current as uniformly as possible throughout the whole of the bath. ith a current of four volts and of a density of 0.3 amps. per square centimetre at the cathode, and of 0.0107

amp. per square centimetre at the anode,

it is possible to ire-oxidize at a temperatureof 30 0., a liquor containing 28.4 grammes of ferrous oxide per litre.

The liquor thus regenerated is poured back on to the residual grey mercury owder, acetylene being then introduced. rom the moment the first bubbles come ofi, the absorption takes place and the production Leashes of acetaldehyde proceeds as intensely and rapidly as if a new catalyzer of mercury adapted to maintain the catalyzing action 7 of the mercury, which comprises removlng the acetaldehyde and mercury from said liquor and submitting the remaining liquor to an oxidizing action.

2. The process for the regeneration of the residua1 reaction liquors obtained in the synthetic production of acetaldehyde from acet lene, in the presence of a mercury cata yzing agent in an acid medium, and of a substance adapted to maintain the catalyzing action of the mercury, which comprises removing the acetaldehyde by the employment of vacuum at a temperature below 50 C., thereupon removing the merc-ury from said liquor and submitting the remaining liquor to an oxidizing action.

3. The process for the regeneration-of the residual reaction liquors obtained in the synthetic production of acetaldehyde from acetylene, in the presence of a mercury catalyzing agent in an acid medium, and of a substance adapted to maintain the catalyzing action of the mercury, which comprises eliminating the acetaldehyde, thereupon precipitating the mercury from said liquor by means of iron filings, decanting the liquor, and subjecting the decanted liquor to an oxidizing action.

4. The process for the regeneration of the residual reaction liquors obtained in the synthetic production of acetaldehyde from acetylene, in the presence of a mercury catalyzing agent in an acid medium, and of a substance adapted to maintain the catalyzing action of the mercury, which comprises eliminating the acetaldehyde by the employment of a vacuum at a temperature below 50 C., thereupon precipitating the mercury from said liquor by means of iron filings at a temperature not exceeding about 70 decanting the liquor and subjecting the decanted liquor to an oxidizing action. A 5. The process for the regeneration of the residual reaction liquors obtained in the synthetic production of acetaldehyde from acetylene, in the presence of metallic mercury, sulfuric acid, and of a ferric compound, which comprises removing the acetaldehyde and mercury from said liquor and oxidizing the ferrous compound to ferric compound.

6. lln the synthetic production of acetaldehyde from acetylene in the presence of metallic mercury in an acid medlum and of a substance adapted to maintain the catalyzing action of the mercury, regenerating the residual reaction liquor, which comprises removing the acetaldehyde and mercury from said liquor, subjecting the remaining liquor to an oxidizing action, and thereupon returning said regenerated liquor to the process to be used again in the synthetic production of acetaldehyde.

' 7. In the synthetic production of acetaldehyde from acetylenein the presence of metallic mercu sulfuric acid, and of a ferric compoun regenerating the residual reaction liquor, which comprises removing the acetaldehyde and mercury from said liquor, oxidizing in the remaining liquor the ferrous compound to ferric compound, and thereupon returning said liquor containing regenerated ferric compound to he process to be used again in the synthetic production of acetaldehyde.

In testimony whereof I have signed this specification in the presence of two subscribing witnesses.

TREVOUX, LAURENT EMILE MARIE Witnesses:

FERNAND DUFOUR, CHARLns LnoN LOISEL. 

